This invention relates to managing an expandable computer bus architecture.
Open system architectures are well known in computer systems. Open computer system architectures are based on the provision of a computer bus which can be expanded by means of expansion cards. In order to provide for computer bus expansion, on a typical backplane, or motherboard, a computer bus will be provided with a number of sockets into which expansion cards can be inserted. There are a number of different standards for computer bus expansions. One conventional standard is the PCI (Peripheral Component Interface) architecture. The PCI architecture enables a bus to be expanded by the insertion of cards, but the standard PCI architecture is less than ideal for a highly reliable system for a number of reasons. Firstly, PCI cards are not hot replaceable, meaning that the cards cannot be inserted when the system is actually running. Accordingly, it is necessary to turn off the main computer system in order to carry out maintenance and insert new cards. Also, it is difficult to tell exactly which card might be generating a fault which can be identified on the bus. Accordingly, this increases maintenance and repairs costs where a fault develops. A further difficulty of PCI cards is the limitation placed on the size of the system which can be produced due to the bus trace length limit for signal propagation. This is a particular problem if easy maintenance is to be enabled. Reliable and easily maintained systems may demand a configuration of bus paths which results in particularly long signal paths. This limits the physical size of the system which can be manufactured due to transmission line factors.